An optical device, a light module and a method for the operation thereof are known in principle from US 2010/0245 777 A1. The latter discloses a light projector including a laser as light source, wherein white light is generated from laser light generated by the laser by means of a phosphor wheel by virtue of the latter rotating and being irradiated by the laser light in a sector. In the circumferential direction the phosphor wheel is coated with different phosphors that convert the laser light into respective conversion light of different other wavelengths. The phosphors of the phosphor wheel are thus arranged successively in the direction of rotation, that is to say in the circumferential direction of the phosphor wheel, such that the light emitted by the respective phosphor, namely the respective conversion light, is generated sequentially in time and is fed to an imaging system. In this case, the temporal succession on account of the rotation of the phosphor wheel and the selection of the phosphors is such that the impression of white light is generated for the human eye. The actual light source is the laser, however, in said document. The technology based thereon is also known under the designation Laser Activated Remote Phosphor (LARP).
In order to distribute the light power of the laser light emitted by the laser over the largest possible area of the phosphor and thus to reduce a thermal stress of the phosphor, inter alia, the phosphor is usually applied to the phosphor wheel, which rotates during operation. During operation as intended, the phosphor is heated on account of the light conversion. The heat is dissipated by radiation, convection and also heat conduction, for example via a shaft of the phosphor wheel, until a steady-state operating temperature is established. The efficiency of the conversion of many phosphors decreases as the temperature of the respective phosphor increases, particularly in the case of nitridic phosphors for the red spectral range. A more than proportional increase in the heat dissipation should thus be taken into account for high light powers. Although this can be compensated for by enlarging the phosphor wheel, this leads to increased costs and larger structural volume.